Game |
| Result | Moves |
Year | Event/Locale | Opening |
1. G Osterman vs K Kaiszauri |
| 0-1 | 38 | 1978 | Rilton Cup 1978/79 | C34 King's Gambit Accepted |
2. L Laurine vs G Osterman |
| 0-1 | 34 | 1978 | Rilton Cup 1978/79 | E75 King's Indian, Averbakh, Main line |
3. G Osterman vs Plachetka |
| 0-1 | 53 | 1978 | Rilton Cup 1978/79 | C36 King's Gambit Accepted, Abbazia Defense |
4. G Osterman vs J Kristiansen |
| 0-1 | 39 | 1978 | Rilton Cup 1978/79 | B80 Sicilian, Scheveningen |
5. J Lind vs G Osterman |
| 0-1 | 24 | 1978 | Rilton Cup 1978/79 | C85 Ruy Lopez, Exchange Variation Doubly Deferred (DERLD) |
6. G Osterman vs K Kaiszauri |
 | 0-1 | 31 | 1980 | Rilton | C34 King's Gambit Accepted |
7. G Osterman vs Y Rantanen |
| ½-½ | 5 | 1990 | Helsinki | B32 Sicilian |
8. Vladimirov vs G Osterman |
| 1-0 | 59 | 1990 | Helsinki | E62 King's Indian, Fianchetto |
9. G Osterman vs T Keskisarja |
| ½-½ | 31 | 1991 | FIN-chT | B36 Sicilian, Accelerated Fianchetto |
10. R Reynolds vs G Osterman |
| 0-1 | 29 | 1993 | ALG jub15 corr9398 | D01 Richter-Veresov Attack |
11. G Osterman vs T Oim |
| 0-1 | 46 | 1996 | FIN-chT 9697 Div-B | C46 Three Knights |
12. J Aijala vs G Osterman |
| ½-½ | 45 | 1996 | FIN-chT 9697 Div-B | C26 Vienna |
13. G Osterman vs M Kurtz |
| ½-½ | 24 | 1996 | John Cleeve Memorial | B81 Sicilian, Scheveningen, Keres Attack |
14. M Nimtz vs G Osterman |
| ½-½ | 38 | 1996 | John Cleeve Memorial | C39 King's Gambit Accepted |
15. G Osterman vs A Hollis |
| 1-0 | 33 | 1996 | John Cleeve Memorial | B81 Sicilian, Scheveningen, Keres Attack |
16. K Tikkanen vs G Osterman |
| 1-0 | 48 | 1996 | John Cleeve Memorial | E59 Nimzo-Indian, 4.e3, Main line |
17. G Osterman vs T Thomas |
| ½-½ | 38 | 1996 | John Cleeve Memorial | B45 Sicilian, Taimanov |
18. G Osterman vs B Zlender |
| 0-1 | 51 | 1998 | John F Cleeve mem | B67 Sicilian, Richter-Rauzer Attack, 7...a6 Defense, 8...Bd7 |
19. G Osterman vs F Brglez |
 | 1-0 | 29 | 1998 | John F Cleeve mem | C41 Philidor Defense |
20. R Hiltunen vs G Osterman |
| 0-1 | 81 | 1998 | John F Cleeve mem | E32 Nimzo-Indian, Classical |
21. A P Borwell vs G Osterman |
| 0-1 | 40 | 1998 | John F Cleeve mem | E32 Nimzo-Indian, Classical |
22. G Osterman vs K E Engel |
| 0-1 | 43 | 1998 | John F Cleeve mem | B93 Sicilian, Najdorf, 6.f4 |
23. J DeMauro vs G Osterman |
| ½-½ | 51 | 1999 | John F Cleeve mem | A62 Benoni, Fianchetto Variation |
24. A Kozlowicz vs G Osterman |
| ½-½ | 61 | 1999 | John F Cleeve mem | C42 Petrov Defense |
25. R A Redolfi vs G Osterman |
| 1-0 | 46 | 1999 | John F Cleeve mem | A09 Reti Opening |